Incandescent electric lamp



July 10,1928.

A. SVED w INCANDESC'ENT ELECTRIC LAMP Fild Feb.-21, 192? Patented July 10, 1928.

UNITED STATES ALEXANDER svnn, or ivnw YORK, N. Y.

INCANDESCENT ELECTRIC LAMP.

Application filed February 21, 1927. Serial No. 168,842.

My invention relates to incandescent electric lamps and hiore particularly to lamps having refractory filaments,'operated in a vacuum or in the atmosphere of any inert 6 gas or vapor.

In my application for Letters Patent for a method of producing high temperatures at a point (application filed simultaneously with this one), I have disclosed a heat and light concentrating unit which in this invention is used to increase the efiiciency of incandescent electric lamps.

My present invention comprises certain improvements whereby the main incandescent body is not operated electrically, thus making possible the use of such materials for illuminating purposes which in themselves are very poor conductors of electricity, or conduct electricity only under certain conditions as for example thoria with 1% ceria. The filament which heretofore was the sole illuminant is used in my invention to give initial light, and to supply heat to the main illuminating body, which under the present arrangement may be operated at a very much higher temperature than the filament, thus increasing the efficiency of the lamp more than 100%.

For a better understanding of my invening drawing in which for purposes of illustration I have shown one of the many arrangements in which my invention may be embodied. Similar numerals refer to similar parts throughout the several views.

In the particular lamp shown in Figure 1 the main illuminating body 1, spherical in form, is placed in the focus of a bifocal reflector 2. The filament 3, held firmly by the filament supports 4, in the focal path of reflector 2. Here again reference is made to my application for Letters Patent for a method of producing high temperatures at a point (application filed simultaneously with this one). The filament 3 is shaped to conform with the configuration of the focal path of the reflector, and it may be made in any form as for example a wire, or coiled into a close helix. The lead 5 is brought down in a glass tube 6 to be connected to the main illuminant support 7, which is made of a stiff, highly refractory material. The

tion reference may be had to the accompanyjoint betweenlead 5 and support 7 is preferably fused into glass tube 6. Lead 8 makes electrical connection with the filament and lead 5. 5

The bifocal reflector 2, highly polished, may be made of any material of good heat and light reflecting properties, is supported by glass rods 9 with the aid of clamps 10 60 riveted to the reflector. Through one of the clamps 10, lead 11 is connected to the reflector so that the electrical connection may be completed by lead 12 to the filament 3. This form of electrical connection is of great value, on account of the additional support given to the filament by the magnetic pull of the electrified reflector, for the sagging of the filament at high temperatures is a common occurrence. If however it is desirable, the lead 11 may be carried directly to .the filament.

Glass tube 13 is the usual support for the internal structure of the lamp, carrying the leads 5 and 11 and the exhaust tube 14. This whole structure as described and shown by the drawing is enclosed in a transparent or semi-transparent envelop 15, made in any desirable form preferablyof glass, to which the screw cap 16 is attached in the usual manner by .cement.

Figure 2 is a transverse section of the internal structure of the lamp between the filament ,3 and therefractory substance 1, looking in the direction of the filament.

In order to prevent the oxidation of the reflector if it is made of metal, and that of the filament it isdesirable that the whole system be operated in a vacuum or preferably in an inert gas such as nitrogen, helium, argon, etc. v

To properly understand the mode of operation of this lamp the following considerations are offered. It is a known fact that in incandescent lamps, even in the most efficient ones, only a comparatively small amount of the electrical energy supplied to the filament is available as light. The greatest portion of the energy supplied is given off as heat by convection and radiation. The filament offers resistance to the flow of the electric current, and in overcoming this resistance a certain amount of energy is expended in the filament when thecurrent is invariably in an attenuated form, is so designed that its radiating surface is not sufficient to give off the heat thus developed at ordinary temperatures. As a result, the filament is overheated and if made of the proper material it becomes incandescent and gives 011' light. Since the rate of radiation depends upon the temperature, theworking temperature of the filament is reached when the energy given ofl' by it is equal to that which is supplied to it by the current.

Guillaumes law states thatthe light given oif varies as the twelfth power of the absolute temperature of the source. From this it is clear, that for maximum efliciency the filament shouldbe worked at the highest v possible temperature.

But at this time filaments are operated at such high temperatures that no further gain in eificiency seems possible, for while it may be possible to' raise the temperature of the filament thelife of the lamp will be greatly reduced. I

In my present invention this difliculty is overcome by employing a main illuminatin body which could be worked at a muc higher temperature than any filament, thus increasing the efliciency of the lamp materially. This is made possible by the fact that the main illuminating body is entirely out of the electrical circuit, and it is used in the spherical form in mass, instead of the attenuated form of a delicate wire. Furthermore the main illuminating body may be made of any material which becomes incandescent at a much. lower temperature, than the material used for filament.

In the common form of incandescent lamps some of the light and heat which is directed toward the sockets is absorbed and wasted in heating up the fixture, and in addition shades are used to direct the light away from the sockets. Some of the light then becomes available as reflected light. In my invention thev light and heat which is directed toward the sockets is utilized to heat the main illuminating body in the following manner. In the lamp depicted in the drawing, when the filament is working heat is radiated and light is emitted in all directions from the filament. The reflector is so designed that exactly one half of the concentrated on the .main illuminating body at the focus. Here specialattention is requested to the unusual design of thereflector which makes this condition possible. (Here again, reference is made to applicathat more than one half of the energy sup plied to the filament will be available for use at the focus.

Radiant energy in itself is cold and heat is manifest only when there is something to receive it. The main iluminating body receives the energy, therefore it becomes heated.

The temperature attained at the focus depends upon the mass and the specific heat of the material used as a main illuminating body, and also upon the rate at which it is capable of giving ofl" heat. The proper proportioning of the size of the main illuminating body therefore is of the utmost importance. v

To form a conception of the size of the main illuminating body let us assume merely as an illustration, that in a 40 watt lamp a tungsten filament and a tungsten main illuminating body are used. According to Langmuir tungsten gives off .441 candle power per square millimeter, and drawn tungsten filaments consume 1.15 watts per candle power, although higherefliciency as been obtained in nitrogen filled lamps. Therefore the lamp produces 34.8 candle powers; and the radiating area of the filament from these figures is roughly 79 s uare millimeters. Since in this particular amp only half the radiations are available at the focus, the radiating surface area of the main illuminating body should be just one half of the total radiating area of the filament (39.5 square millimeters), in order to give off the energy at the same rate and temperature as it is supplied to it by the filament. It has been stated that the shape of the main illuminant is spherical. A sphere with 39.5 square millimeters radiating surface has a diameterv of 3.4 millimeters roughly.

If the diameter of the sphere is slightly reduced its radiating area becomes smaller, and in order to give off the heat as fast as it is supplied to it, the main illuminating body must assume a. higher temperature than the filament. At a higher temperature the efliciency is greatly increased.

The melting point of tungsten according to Langmuir is 3267 degrees centigrade, and

the working temperature of the filament is 2150 degrees centigrade v(in nitrogen filled lamps higher, but the same reasoning applies). The main illuminating body being in the mass, and not in the fine wire form, can safely be heated 300 degrees centigrade higher than the filament. An increase of 300 degrees centigrade in temperature will give about 4.4 times the amount of light than the half filament, or 2.2 times as much as the whole filament. Considering that one half the light given ofi' by the filament is availhalves) that given off by the whole filament. 5 Accounting for losses due to heatingof the reflector and due to the reduction of the radiating area of. the main illuminating.

body, instead of 150% increase in efliciency, we ma only expect 100%. v In t is demonstration it was shown that In vacuum lamps 100% increase in efficiency may easil be obtained. The same increase may be tained in nitrogen lamps or any other lamps, provided the same material is used for both the filament and the main illuminating body. But b this method we are not limited in the se ection of the material for the main illuminating body to good electrical conductors. Therefore any material which becomes incandescent when heated may be used. Furthermore we may select a material which becomes incandescent ,at a much lower temperature than the filament, as for example thoria with 1% ceria, which at the same time may withstand an increase of 500 to 600 degrees centigrade, thus increasing the efliciency 200 or 300%.

In these lamps several seconds elapse before full illuminating power is reached, and depending upon the design and materials used the pick up varies between 5 and 8 seconds, but it must be bornein mind that immediate light is given off by the half filament. p In order to reduce the heating effect on the reflector its convex surface may be roughened so that it may give off the absorbed heat with greater facility.

What I claim is new and desire to obtain by Letters Patent of the United States is:

1. An incandescent electric lamp comprising' a sealed bulb; a highly polished metal reflector, formed by revolving a bifocal,segment about an axis at an angle to a line passing through thetwo foci, the said axis passing through one of the foci; a refractory metal filament placed exactly into and shaped to conform with the configuration of the focal path of the reflector; and a mass of refractory substance of. proper dimensions placed atthe common focus of the said reflector. t r

v 2. An incandescentelectrit: lamp comprising a sealed bulbfa highly polished metal re e ment about an axis at an angle to a line passing through the two foci, the said axis passing through one of'the foci; a refractory lament placed exactl into and shaped to conform with the con guration of the focal path of the said reflector, to give initial light and to supply heat to amass of refractory substance of fproper dimensions, placed at the common. cons of the reflector.

w 3. An incandescent electric lamp compristhe filament.

ctor, formed by revolving a bifocal seg-- in a sealed bulb; a highly polished metal re ector', formed by revolving a bifocal seg ment-alrout, anaxis at an angle to a. line passing through the two foci, said axis passing through one of the foci; a refractory filamentplaced exactly into and shaped to conform with the configuration of the focal path, of the reflector; and a mass of refractory substance of properldimensions which is the main illuminating element of the lamp, laced at the common focus of the said re 'ector. 4. An incandescent electric'lam compris ing a sealed bulb, a highly'polis ed metal reflector, formed by revolving a bifocal segment about an axis at an angle to a line pass ing through the two. foci, said axis passin through one of the foci; a refractory. meta filament placed exactl into andshaped to conform with the confl uration of the focal path of the reflector; and a. mass of refractory substance of proper dimensions placed at the common focus of the reflector, which can be worked at a higher temperature than x 5. An incandescent electric lamp, compris-v ing a highly polished metal reflector, formed by revolvin a bifocal segment about an axis at an angle to a line passlng through the two foci, said axis passing through one of the foci; a refractory metal filament placed exactly into and shaped to conform with the configuration of the focal path of the reflector; and a mass of highly refractory substance placed at the common focus of the reflector'; all within a. sealed bulb filled with an inert gas.

6. An incandescent electric lamp comprising a sealed bulb, an electrified metal reflector, formed by revolving a bifocal segment m5 about an axis at an angle to a line passing. through the .two. foci, said axis passing throughone of the foci; a refractory metal filament placed exactly into and shaped to conform with the configuration of the focal no path of the reflector, and a mass of highlyre fractory substance 'of proper dimenslons placed at the common focus of the reflector.

7. An incandescent electric lamp comprising a sealed bulb, a metal reflector, having a highly polished reflecting .surface and a roughened convex surface, formed by revolving a bifocal segment about an axis at an angle to a line passing through the two foci, said axis passing throughone of the foci; a refractory metal filament placed exactly into and shaped to conform with the configuration of the focal path of the reflector, and a mass of highly refractory substance of a I proper dimensions placed at the common focus of the reflector.

8. An incandescent electric lamp compris-.. ing a sealed bulb; a. highly polished metal r-. flector, formed by revolving a bifocal segme t abeut an ax s atan a g e o a n pass- 1:0.

refractory substance spherical ing through the two foci, said axis passing through one of 'thefoci; a refractory metal filament placed exactly into and shaped to conform with the configuration of the focal path of the reflector, and a mass of highly in form,

' placed at the common focus of the reflector.

9. An incandescent electric lamp comprising a sealed bulb; a highlypolished metal reflector, formed by revolving a bifocal segment about an axis at an angle to a line passing through the two foci, said axis passing through one of the foci; a refractory metal .of a sealed bulb, a highly polished metal reflector, formed by revolving a bifocal segment about an axis at an angle to a line passmg through the two foci, said axis passing neraaoo through one of the foci; a refractory metal 11. An incandescent electric lamp comprising a sealed bulb; a highly polished metal reflector, formed by revolving a bifocal segment about an axis at an angle to a line passing through the two foci, said axis passing through one of the foci; a refractory metal filament placed exactly into and'shaped to conform with theconfigura'tion of the focal path of the reflector, and a mass of refractory substance of proper dimensions placed at the common focus of the reflector, which becomes incandescent at a much lower temperature than the working temperature a of the filament.

Signed at New York in the county of New York and State of New York this 17th day of February A. 10.1927.

ALEXANDER SVJED. 

